Adhesives are applied to substrates and are widely used for various commercial and industrial applications, such as product assembly and packaging.
Hot melt adhesives are widely used in the packaging industry to seal cardboard cases, trays and cartons. Some packaging applications require an adhesive to maintain a strong bond to a substrate under extremes of stress and shock in handling, and high temperatures and humidity. Moreover, cases and cartons often encounter very high temperatures during transportation, so adhesives having sufficiently good heat resistance are required in these applications. “Sufficiently good heat resistance” is to be understood to mean that the bonded adhesive maintains fiber tear at elevated temperature, e.g., greater than 52° C. (125° F.), and hence should not immediately soften when acted upon by elevated temperature, with the result that the adhesive bond loosens and/or the bonded parts shift with respect to one another.
Recent developments in polymer technology have allowed for a new generation of propylene with various comonomer based adhesives. However, such adhesives typically have long set-time. For fast throughput, packaging manufacturers desire adhesives with short set-time.
To increase throughput, a nucleator is added to polypropylene-based hot melt adhesive to speed the crystallization time (set-time) in US2005/0288412. However, the drawback to this approach is that the heat resistance of the adhesive can also decrease.
There is a need in the art for a hot melt adhesive that possesses good high heat resistance and fast set-time performances. The current invention fulfills this need.